Reptiles

Crocodiles, too, regulate their body temperature on land by varying their position relative to the Sun's rays. They also open their mouths to increase heat loss by evaporation. If the temperature becomes too high, they move into the water which is relatively cooler. At night they retreat to water in order to avoid the low temperatures which would be experienced on land. Regularization mechanisms have been studied most extensively in lizards. Many different species of lizard have been studied and show a variety of responses to different temperatures. Lizards are terrestrial reptiles and exhibit many behavioral activities, as is typical of other isotherms. Some species, however, use a number of physiological mechanisms to raise and maintain their body temperatures above that of the environment. Other species are able to keep their body temperature within confined limits by varying their activity and taking advantage of shade or exposure. In both these respects lizards foreshadow many of the mechanisms of thermometer shown by birds and mammals. 

Surface temperatures in desert regions can rise to 70-80 °C during the day and fall to 4 °C at dawn. During the periods of extreme temperatures, most lizards seek refuge by living in burrows or beneath stones. This response and certain physiological responses are shown by the horned lizard (Chromosomal) which inhabits the deserts of the south-west of the USA and Mexico. In addition to burrowing, the horned lizard is able to vary its orientation and color, and as the temperature becomes high it can also reduce its body surface area by pulling back its ribs. Other responses to high temperatures involve panting, which removes heat by the evaporation of water from the mouth.